Method and system to reduce polluting emission from internal combustion engines

ABSTRACT

After the engine has started, and while it is still cold and before it has warmed up, the ignition is delayed in addition to the normal delay to such an extent that combustion of fuel will persist during the exhaust stroke of the engine to accelerate the warm-up time of the exhaust system of the engine; this delay may be set in the range of from 10* to 25* after deadcenter of the piston during the power stroke. When the engine, or the exhaust system, or components thereof have reached a predetermined temperature, ignition timing is then controlled as usual.

Eichler et a1.

[75] Inventors: Dieter Eichler, Hochberg; Otto Glockler, Renningen; Richard Bertsch, Asperg, all of Germany [73] Assignee: Robert Bosch Gmblli,

Gerlingen-Schillerhohe, Germany [22] Filed: June 29, 1972 [21] Appl. No.: 267,562

[30] Foreign Application Priority Data Jan. 21, 1972 Germany 2202786 [52] [1.5. CI. 123/117 R, 123/117 A [51] Int. Cl. F02p 5/04 [58] Field otSearch 123/117 R, 117 A, 119D [56] References Cited UNITED STATES PATENTS 3,426,737 2/1969 Walker 123/117 A 3,447,518 6/1969 Walker 123/117 A 3,515,368 6/1970 Kelly 123/117 A Feb. 11., 1975 3,561,410 2/1971 soeters 123/117 A 3,603,298 9/1971 3,626,909 12/1971 Hayushlda [23/117 A 3,631,845 l/l972 Walker 3,670,709 6/1972 Eckert 3,687,120 8/1972 Lenz 3,707,954 l/l973 Nakada 123/117 A Primary E.\'aminerCharles J. Myhre Assistant Examiner-Cort Flint Attorney, Agent, or Firm-Flynn & Frishauf [57] ABSTRACT After the engine has started, and while it is still cold and before it has warmed up, the ignition is delayed in addition to the normal delay to :such an extent that combustion of fuel will persist during the exhaust stroke of the engine to accelerate the warm-up time of the exhaust system of the engine; this delay may be set in the range of from 10 to 25 after deadcenter of the piston during the power stroke. When the engine, or the exhaust system, or components thereof have reached a predetermined temperature, ignition timing is then controlled as usual.

19 Claims, 17 Drawing Figures PATENTEB FEB I 1 I975 smin s or 5 11 METHOD AND SYSTEM TO REDUCE POLLUTING EMISSION FROM INTERNAL COMBUSTION ENGINES Cross reference to related patent and applications: US. 3,483,851, Reichardt, December 16, 1969.

The present invention relates to a method, and to a system to reduce noxious components in the exhaust emission of internal combustion engines, and more particularly to reduce the noxious components which arise during warm-up time of the engine.

Internal combustion engines require higher and higher standards of reduced polluting emission. In one system, utilizing electronic fuel injection, the air-fuel mixture is matched to the various operating parameters of the internal combustion engine and, indeed, also to ambient parameters within which the engine operates, such as ambient air pressure or the like. With such systems, the air-fuel ratio can be so set that the combustion is an optimum. Electronic fuel injection systems have lower polluting emissions during normal operation of the engine than carburetor-type engines; however, it has been shown that polluting exhaust during the start-up time of the engine, and during the warm-up period of the exhaust system is particularly high. Tests have shown this comparatively large polluting component during warm-up, for example the well known CVS (constant volume sampling) test. A comparatively large portion of the noxious components in the exhaust gases are generated during the warm-up phase of the engine.

It is an object of the present invention to provide a method, and a system utilizing the method which is particularly suited to effectively reduce the polluting components in the exhaust emission of internal combustion engines during the warm-up period of the engine system, and particularly of the exhaustportion thereof. Subject matter of the present invention Briefly, upon starting of the engine, and particularly after the engine has started and runs smoothly and without bucking, the ignition timing of the ignition system of the engine is changed to be delayed to such an extent that combustion of the fuel will be extended and may, for example, even persist during the exhaust stroke of the engine. Preferably, the ignition timing is delayed to to 25 of crankshaft angle after the upper dead-center of the piston in the cylinder. This delay is then reduced and removed to the normal ignition timing control when a component of the engine system, typically the exhaust system of the internal combustion engine has a predetermined temperature.

The system of the present invention can be made inexpensively and can be utilized as an adaptation to existing engines, while operating reliably. The system, in accordance with a feature of the invention, utilizes the normally employed and well known vacuum diaphragms to change the position of a timing disk in the distributor by means of an adjustment rod. The movement of the adjustment rod, setting the delay of the ignition timing is controlled by a stop which limits the excursion of the adjustment rod, the stop changing position in dependence on the operating temperature arising within the engine system, and more particularly within the exhaust system of the internal combustion engine.

Reference in the specification will be made to the air number, denoted lambda (A). This air number A is a measure ofthe composition of the air-fuel mixture. The

number A is proportional to the mass of air and fuel, and the value of this number A is one (A 1.0) if a stoichiometric mixture is present. Under stoichiometric conditions, the mixture has such a composition that, in view of the chemical reactions, all hydrocarbons in the fuel can theoretically combine with the oxygen in the air to provide complete combustion to carbon dioxide and water. In actual practice, even with a stoichiometric mixture, unburned non-combusted hydrocarbons and carbon monoxide are contained in the exhaust gases.

The invention will be described by way of example with reference to the accompanying drawings. wherein:

FIG. 1 is a diagram indicating the influence of the air number A to the exhaust emissions of an internal combustion engine;

FIG. 2 is a schematic showing of the ignition distributor retardation system, with a vacuum chamber shown in greater detail in section, to retard the ignition during warm-up of the engine;

FIG. 3 is a schematic graph indicating change in ignition timing in dependence on speed and inlet manifold vacuum; I

FIG. 4 is a graph indicating change in ignition timing with partial loading and idling of the engine, when cold;

FIG. 5 is a graph similar to FIG. 4, but when the engine has warmed;

FIG. 6 is a diagram similar to FIG. 2, and illustrating a different embodiment;

FIG. 7 is a graph similar to FIG. 3 and indicating igni tion change with respect to speed and inlet manifold vacuum of the system of FIG. 6;

FIG. 8 is a diagram similar to FIG. 5 illustrating change in ignition timing in a partially loaded and in an idling engine, when cold;

FIG. 9 is a graph similar to FIG. 8 with the engine warm;

FIG. 10 is a schematic diagram similar to FIG. 2 and illustratihg another embodiment;

FIG. 11 is a graph similar to FIGS. 3 and 7, but with respect to the embodiment of FIG. 10;

FIG. 12 is a graph similar to FIGS. 4 and 8 but with respect to the system of FIG. 10;

FIG. 13 is a graph similar to FIGS. 5 and 9, but with respect to the system of FIG. 10;

FIG. 14 is an illustration similar to FIG. 2, but illustrating a different embodiment;

FIG. 15 is a graph similar to FIGS. 3, 7 and 10, but with respect to the embodiment of FIG. 14;

FIG. 16 is a graph similar to FIGS. 4, 8 and 12, but with respect to the system of FIG. 14; and

FIG. 17 is a graph similar to FIGS. 5, 9 and 13, but with respect to the embodiment of FIG. 14.

The graph of FIG. 1 illustrates the emission of nitrogen-oxygen compounds, hydrocarbons, and carbon monoxide with respect to air number A. Curve 20 illustrates the nitrogen-oxygen compounds No,, curve 21 illustrates emission of unburned hydrocarbons, and curve 22 emission of carbon monoxide. The air number )t 1 when a stoichiometric fuel-air mixture is present, which is, usually, by mass, about I to 14.4 for gasoline internal combustion engines. The curves clearly show that the CO emission decreases as It increases; the C-H emission decreases until I has a value of about 1.1, then is essentially horizontal, and as I increases even more, the unburned hydrocarbon emission increases again. The NO, emission increases rapidly at a value of about A 1.0 and has a maximum at about A 1.1.

Thereafter, the NO, emission again is reduced substantially. The curves of FIG. 1 are drawn for a fully loaded, warm internal combustion engine, at operating temperature. Upon starting, and during warm-up of the engine, and when the exhaust system is still cold, the exhaust emission of CO and unburned hydrocarbons is substantially increased. It is therefore desirable that the exhaust system of the internal combustion engine be warmed as soon as possible, and particularly when thermal and catalytic reactors (or only catalytic reactors) are used, so that carbon monoxide and hydrocarbons can be reduced by reacting the carbon monoxide and the hydrocarbons after they have been emitted from the cylinder of the internal combustion engine.

Delaying the ignition to an extreme extent, for example in the region of 10 to 25 after the upper deadcenter position of the piston of the internal combustion engine has the effect that when the exhaust valve opens, the combustion of the fuel has not completely terminated yet, thus rapidly heating the exhaust system. Flames may actually penetrate into the exhaust system of the internal combustion engine, to rapidly heat the exhaust manifold and the surrounding parts. The extreme delay of ignition decreases the thermal efficiency of the internal combustion engine, which substantially decreases the NO, emission. After the exhaust system has heated and has reached a predetermined temperature, which is sensed by a thermostat, the additional and extreme delay in ignition can be reduced so that the output manifold will not reach a temperature which is excessive and which may cause damage.

Referring now to FIG. 2, wherein a system to carry out the invention is illustrated: The ignition timing is delayed to about 10 to 25 after the upper dead-center position of the piston in the cylinder. FIG. 2 illustrates, schematically, the adjustment disk 23 of a distributor for an internal combustion engine. This adjustment disk 23 is operated over a rod 24 by an' ignition delay chamber 25 and an ignition advance chamber 26. The delay chamber 25 can be utilized to retard the spark during idling, in order to improve the emissions during idling. By setting the spark about delayed, that is, 5 after dead-center, the combustion within the combustion chamber of the engine is retarded to such an extent that the exhaust will, even when the engine is idling, reach a sufficient temperature which is desirable to reduce exhaust emission. The delay by the chamber 25 is limited by means of a stop 27 which engages in a notch 28 of rod 24.

Spark advance chamber 26 operates, as well known, to advance the spark at partial loading.

In order to obtain a further delay of the spark to a region of from to after dead-center, the stop 27 is formed to be movable, preferably by being controlled by an electromagnet or solenoid coil 29. Upon operation of coil 29, stop 27 is withdrawn from notch 28 of rod 24, so that the rod 24 can travel over a greater path, in order to still further delay the ignition timing. Magnet 29 is operated by a temperature-sensitive switch 30 which is in thermal conductive relation to the exhaust system, schematically indicated as manifold E in FIG. 2, and which is thus operated when the exhaust manifold reaches a predetermined temperature. Thermostat switch 30 can physically be mounted'in contact with the exhaust system, as illustrated at 30, or can be separately operated.

When the thermostatic switch 30 is in a first position. that is, during warm-up and before the exhaust system E has reached the predetermined temperature, switch 30 is closed, and electromagnet 29 is operated, that is, stop 27 is pulled in. This permits extreme delays by the delay chamber 25 during the warm-up time of the engine. Switch 30 additionally controls a valve 31 which interconnects the delay chamber 25 with the suction side of the inlet manifold during the warm-up time of the exhaust system. The advance chamber 26 is separated from the inlet manifold, or the suction portion thereof during warm-up of the exhaust system.

The temperature-sensitive switch 30 additionally controls an auxiliary valve 33 which is connected in a bypass to the throttle 34 in the inlet manifold 35 of the internal combustion engine. The bypass to throttle 34 is provided so that the idle speed does not decrease when the ignition timing is delayed by extreme values. During the warm-up of the exhaust system, the auxiliary control valve is opened, so that the bypass to throttle 34 is opened. After the engine has warmed up, the additional valve is closed and thus the bypass to throttle 34 is likewise closed. The stop 27 is again engaged so that the maximum ignition delay may be only 5, upon idling. Additionally, after warm-up and after the exhaust system has reached its operating temperature, the temperature-sensitive switch 30 will control the control valve 31 to change to its second switching position in which the spark advance chamber 26 is connected with a port 36 located adjacent the throttle 34 in the inlet manifold, or as part of the carburetor assembly. Further, the delay chamber 25 is connected to a port 37 in the inlet tube, or the carburetor, which is likewise located close to the throttle 34.

The ports are usually located in a portion of the carburetor assembly, for example a throttle body thereof.

FIG. 3 illustrates the change of the ignition timing with respect to engine speed, or with respect to inlet manifold vacuum, respectively. The ordinate illustrates, in degrees with respect to dead-center, the ignition timing, delay being below zero and advance being above'zero. As can be seen from curve 38, at low speed there is little spark advance; as the the speed increases, that is, in intermediate speeds, the spark advances gradually and at high speed remains constant, and advanced. Curve 39 illustrates spark advance at partial loading. Curve 40 illustrates spark retardation or delay with respect to vacuum in the inlet manifold. As shown, delay of the ignition occurs only when a predetermined vacuum is sensed, this delay, as above referred to, being roughly 5 after dead-center. Curve 41 shows the extreme delay warm-up of the exhaust system of the internal combustion engine. As seen, the change first is similar to that of curve 40; yet, at the point where with curve 40 the stop 27 would engage, the curve, nevertheless,, continues since, in warm-up, stop 27 has been withdrawn so that further spark delay is possible.

FIG. 4 illustrates the spark advance curve 38, for full load operation. Curve 43 illustrates the characteristic of change in ignition timing for partial or for idling, when the engine is cold. Curve 43 illustrates that it is practically parallel to the spark advance curve 38 (in dashed line), the distance between the two curves 38 and 43 being determined by the extreme time delay during warm-up of the exhaust system of the internal combustion engine.

FIG. 5 illustrates the full load spark advance characteristic 38, in broken lines. Additionally, a graph 44 is shown which is representative of partial loading and idling when the internal combustion engine has reached operating temperature. This curve shows that when the internal combustion engine is warm, delay is effective only when the throttle is closed; as soon as the throttle is opened and the engine has reached speeds which are above the idling speed, the idling delay is disconnected and the partial load spark advance becomes effective.

FIGS. 3, 4 and 5 have their abscissas drawn to the same origin, that is, the zero angle is offset for clarity.

FIG. 6 illustrates a different embodiment of the present invention in which similar and similarly operating components as those in the embodiment of FIG. 2 have been given the same reference numerals, and will not be described again in detail.

The change in the position of the stop member 27, as well as the change-over of the auxiliary valve 33 is accomplished pneumatically, rather than electrically as in the example of FIG. 2. Stop member 27 fits within the notch 28 of the operating rod 24 between the distributor advance-retard setting disk 23 and the advanceretard chamber or diaphragm assembly 25, 26. The

stop 27 is changed in position in dependence on the pressure, or rather vacuum arising within diaphragm chamber 42. The additional valve 32 itself is changed by a vacuum diaphragm chamber 45 in its position. Both of the vacuum diaphragm chambers 42, 45 are controlled by a vacuum line 46, connected to control valve 47 which interconnects the vacuum chambers 42, 45 with the suction port 32 within the suction system of the internal combustion engine during the warm-up period of the engine. The control valve 47 additionally provides a connection from the start delay or retard chamber 25 to the suction chamber 32 during the warm-up period of the exhaust system of the engine. The spark advance chamber 26, during this warm-up period of the exhaust system, is connected with a vent bore 48 in the control valve 47, so that the spark advance chamber 26 is unloaded and cannot effect any change of the position of the operating rod 24.

After the exhaust system has warmed up, control valve 47 is changed over in its position by the temperature sensing switch 30, so that the spark advance chamber 26 is connected with the port 36 in the inlet or suction portion 35 leading to the engine, close to the throttle 34. Further, the second position of the control valve 47 interconnects line 46 with the vent bore 48 of the control valve, so that both spark retard chambers 42 and 45 are vented and unloaded. Further, the second position of the control valve 47 interconnects the spark delay chamber 25 with a bore 38 in the vicinity of the throttle 34, within the inlet suction system of the internal combustion engine.

The characteristics of the ignition timing, resulting from this arrangement, are similar to those of FIGS. 3, 4 and 5, corresponding to the arrangement of FIG. 2. FIG. 7 illustrates the full load characteristic curve 38 for spark advance; curve 39 illustrates the spark advance characteristic at partial load. Further, characteristic curves 40 and 41 illustrate the spark retardation, curve 41 illustrating the extreme retardation during warm-up of the exhaust system. FIG. 8 illustrates, in broken line curve 38, the entire characteristic, which is similar in shape to the characteristic curve 49, which is again similar to curve 43 of FIG. 4. As can be seen, during warm-up, extreme retardation of the spark is effected, in that the stop 27 is withdrawn from notch 28 of rod 24. The retardation is superimposed to the full load characteristic curve 38, which is the curve governed by the centrifugal control of spark timing, so that the overall characteristic of curve 49 is similar, in shape and appearance, to that of the full load characteristic 38.

The broken line curve 38 of FIG. 9 again represents the full load characteristic, and is shown together with the overall characteristic 50, which corresponds to the overall curve 44 in FIG. 5.

Embodiment of FIG. 10: The distributor timing plate 23 is connected over operating rod 24 with three vacuum chambers. The rod 24 can change position depending on the relative pressures within spark advance chamber 51, spark retardation chamber 52 and additional retardation chamber 53. The usual idling retardation is carried out by means of the retardation chamber 52, which is fitted against a plate 54 acting as a stop member. During warm-up of the exhaust system of the internal combustion engine, when the ignition should be retarded additionally further, the membrane 55 of the additional chamber 53 moves towards the right, counter the force of a spring 56, so that the stop of the normal retarding position of chamber 52 is changed. These two movements are superimposed. The normal idling retardation, commanded by chamber 52, and the additional retardation commanded by chamber 53 provides for a larger position change of rod 24 and thus for a greater delay of the ignition timing.

The various chambers 51, 52, 53 are controlled from a control valve 57 which, in dependence on the position of the temperature sensitive switch 30 has two different control positions. During warm-up of the exhaust system of the internal combustion engine, the additional chamber 53 is connected over control valve 57 with the suction distributor 32 in the suction system of the internal combustion engine. The idling retardation chamber 52 is directly connected to bore 37 in the inlet tube 35, in the vicinity of the throttle 34. The spark advance chamber 51 is connected with a vent bore 58 during warm-up of the exhaust system of the engine and is separated from the suction system of the internal combustion engine by the control valve 57. During warm-up of the exhaust system, a bypass is connected in parallel to throttle 34, the bypass being controlled by auxiliary valve 33 which opens a line from a bore 59 located in advance to the throttle in the inlet tube throttle body of the carburetor, and adjacent the throttle 34, and connects with the inlet manifold 32.

Operation: After warm-up, and when the control valve 57 has been switched over to its second switching position, that is, when the exhaust system is at operating temperature, the bypass to the: throttle 34 is closed by means of the chamber 45. The additional chamber 43 is separated from the inlet manifold 32 and con nected with the vent bore 58. The spark advance chamber 51 is connected to bore 36 located close to the throttle 34 in the throttle body of "the inlet to the internal combustion engine.

The characteristics resulting from this operation are seen in FIGS. 11-13 and, as is apparent, are similar to the characteristics previously discussed. In FIG. 11, curve 38 illustrates the full load relationship; curve 39 the partial load spark advance. Cuzrve 40 illustrates the spark retardation at idling, curve 59 illustrates the spark retardation when the motor is cold. The curve 59 illustrates that, at a predetermined inlet manifold pres sure, the spark retardation is effective'to a greater extent than in the examples of FIGS. 2 and 6, as indicated by the steeper portion of the curve at 60. This more rapidly acting retardation of the spark is obtained by superimposition of the movement of the idling spark retard chamber 52 with the additional chamber 53.

The full load characteristic 38 is again shown in FIG. 12; the ignition distributor characteristic 61 is illustrated for idling and partial load operation, with the engine cold. As can be seen, at idling, an extreme ignition retardation is obtained. As the throttle is opened, the under-pressure for the spark retardation chamber 52 drops, so that at partial loading only the retardation due to the additional chamber 53 is effective which, again, is superimposed over the full load characteristic 38, and is thus parallel thereto.

FIG. 13 illustrates the full load characteristics at 38 in broken lines and, in curve 62, illustrates the total change in position of the ignition timing in partial load and idling operation when the engine is warm. As can be seen, curve 62 is shifted with respect to curve 61 by the value of the additional time delay of the cold internal combustion engine, and by the partial load spark advance.

Embodiment of FIG. 14: The distributor ignition timing disk 23 again is changed in position by adjusting rod 24, which is commanded by a spark advance chamber 51, idling retardation chamber 52 and additional chamber 53. The interconnection between the chambers 51, 52 and 53 with the vacuum system of the internal combustion engine is effected over a control valve 63. The first position of valve 63, as shown in the drawing, corresponds to a position in which the exhaust system has not yet reached operating temperature, whereas change-over to the second switching position occurs when the temperature sensitive switch 30 has operated. In the first switching position, control valve 63 interconnects the idling retardation chamber 52 and the additional chamber 53 with the inlet manifold 32 of the internal combustion engine. The spark advance chamber 51 is connected with a vent bore 64. A bypass, in parallel to throttle 34, is controlled by auxiliary valve 33. It is opened by chamber 45, controlled by the valve 63, by being connected by valve 63 with the inlet manifold 32 of the internal combustion engine. The idling retardation chamber 52 and the additional chamber 53 are similar to the embodiment of FIG. 10.

After the warm-up of the exhaust system of the internal combustion engine, switch 30 will change over and valve 63 will assume its second switching position, in which the spark advance chamber 51 is connected with bore 36 in the throttle body of the carburetor.

The characteristics of the arrangement of FIG. 14 are illustrated in FIGS. to 17. The full load characteristic 38, and the partial load characteristic 39 are similar to those of FIG. 11. Likewise, the delay curves 40 of the idling delay and curve 59, with the steeper portion 60 representative of the additional delay during warmup are similar to the characteristics illustrated in FIG. 11. FIG. 16 illustrates in curve 38 the full load line when the engine is cold, and at curve 65 the overall characteristics upon partial loading or idling with cold engine. The difference between curve 65 (FIG. 16) and curve 61 (FIG. 12) arises in the interconnection of the common spark idling delay chamber 52. In the embodiment of FIG. 10, the spark idling delay chamber 52 is connected at all time with bore 37 located close to throttle 34 in the throttle body of the internal combustion engine; in the arrangement in accordance with FIG. 14, however, the idling retardation chamber 52, during warm-up of the engine, is connected with the inlet manifold 32 of the internal combustion engine and after warm-up is connected to bore 37 located close to the throttle 34 in the throttle bottle of the carburetor or the inlet to the engine.

FIG. 17 illustrates, again in broken line at curve 38, the full load characteristics with the warm engine and curve 66 the overall change of the ignition timing upon partial load and idling with warm internal combustion engine.

The present invention has been illustrated in connection with a specific arrangement to change the position of the distributor timing; various and modifications may be made within the inventive concept.

The present invention has been illustrated in connection with highly schematic drawings. For a complete discussion of operating parameters and spark advance and retardation, reference is made to Principles of Automotive Vehicles, US. Government Publication TM 9-8000, chapter on Battery Ignition," with the proviso that the linkages interconnecting vacuum chambers to the breaker plate or element determining ignition timing should be capable of turning the plate so that the spark can be retarded for a greater degree than heretofore customary in internal combustion engines.

We claim: 1. System to reduce polluting components from the exhaust of internal combustion engines during warmup of the engine, in combination with an engine having an inlet manifold, a throttle, timing control means operable within a predetermined range for timing the ignition of the engine, within said range, with respect to piston position, and an exhaust system including an exhaust manifold, said pollution reducing system comprising means (25, 26, 51, 52) continuously effective during engine operation to adjust the ignition timing of the ignition system within said range, comprising a spark advance vacuum chamber means (25, 26) to advance or delay ignition timing within said range with respect to dead-center position of the piston;

adjustment link means (24) connected to the ignition timing adjustment means;

means controlling additional retardation of ignition timing of the ignition system, to a delay value of such magnitude that combustion will persist during at least a portion of the exhaust stroke of the engine in addition to the adjustment of the ignition timing, within said range, due to said continuously effective ignition timing means, comprising a control valve (31) interconnecting the spark delay chamber (25) to the inlet manifold of the engine during warm-up time of the engine and before the engine has reached said predetermined temperature, said valve (31) connecting the delay chamber to a suction port (37) located in the vicinity of the throttle (34) in the inlet to the engine;

and means (30) responsive to temperature arising in the exhaust system of the engine during operation thereof, said temperature responsive means including means controlling the extent of travel of said link element to disable control by said additional ignition timing retardation means when said temperature responsive means senses that a predetermined temperature is exceeded.

2. System according to claim 1, wherein the means additionally retarding ignition timing of the ignition system comprises a link element (24) connected to adjust the timing of the ignition with respect to piston position;

and means including stop means (27; 54) controlling the path of travel of said link element (24) under control of said temperature responsive means (30).

3. System according to claim 2, wherein the stop means comprises electromagnetically controlled means (29).

4. System according to claim 2, wherein the stop means include vacuum diaphragm chamber operated means (42).

5. System according to claim 4, wherein the temperature responsive means provide an output signal controlling a valve means, said valve means selectively connecting fluids under differential pressure to said vac uum chamber means.

6. System according to claim 2, wherein said link element (24) is formed with a notch (28), said stop means (27) engaging in the notch.

7. System according to claim 2 wherein the means continuously effective during engine operation to adjust ignition timing within said range comprises a spark advance vacuum chamber and a spark delay vacuum chamber;

and the stop means controlling the path of travel of said link element (24) comprises a movable abutment (54) on said spark delay vacuum chamber movable in dependence on sensed temperature by said temperature responsive means (30) in the direction of said path.

8. System according to claim 1, wherein the means continuously effective during engine operation to adjust ignition timing within said range comprises a spark advance vacuum chamber and a spark delay vacuum chamber;

and wherein the means additionally retarding ignition timing further comprises a vacuum bore (36) located in the inlet (35) to the engine, and means interconnecting said vacuum bore (36) with the spark advance chamber (26);

and valve means (31) separating the spark advance chamber from said bore until the engine has reached said predetermined temperature.

9. System according to claim 8, further comprising means (57) interconnecting the ignition delay chamber (53) with the inlet manifold (32) ofthe engine until the engine has reached said predetermined temperature.

10. System according to claim 1, wherein the means continuously effective during engine operation to adjust ignition timing with said range comprises a spark advance vacuum chamber (51) and a spark delay vacuum chamber (52); and

a control valve (57; 63) selectively venting said chambers.

11. System according to claim 10, wherein said igni- HOT] tlmll'lg retardation means comprises a vacuum chamber (53), said valve meas selectively venting said vacuum chamber.

12. System to reduce polluting components from the exhaust of internal combustion engines during warmup of the engine, in combination with an engine having an inlet manifold, a throttle, timing control means operable within a predetermined range for timing the ignition of the engine, within said range, with respect to piston position, and an exhaust system including an exhaust manifold, said pollution reducing system comprising means (25, 26, 51, 52) continuously effective during engine operation to adjust the ignition timing of the ignition system within said range, comprising a spark advance vacuum chamber and a spark delay vacuum chamber;

means (31, 33) controlling additional retardation of ignition timing of the ignition system, to a delay value of such magnitude that combustion will persist during at least a portion of the exhaust stroke of the engine in addition to the adjustment of the ignition timing, within said range, due to said continuously effective ignition timing means, and including a vacuum bore (36) located in the inlet (35) to the engine, means interconnecting said vacuum bore (36) with the spark advance chamber, and valve means (31) separating the spark advance chamber from said bore until the engine has reached a predetermined temperature;

and means (30) responsive to temperatures arising in the exhaust system of the engine during operation thereof, said temperature responsive means controlling operation of said valve means (31) to disable control by said additional timing retardation means when said temperature resonsive means senses that the predetermined temperature is exceeded.

13. System according to claim 12, further comprising means (57) interconnecting the ignition delay chamber (53) with the inlet manifold (32) of the engine until the engine has reached said predetermined temperature.

14. System according to claim 12, wherein the means additionally retarding ignition timing of the ignition system comprises a link element (24) connected to adjust the timing of the ignition with respect to piston position;

and means including stop means (27; 54) controlling the path of travel of said link element (24) under control of said temperature responsive means (30).

15. System according to claim 12, wherein the means continuously effective during engine operation to ad just ignition timing within said range comprises a spark advance vacuum chamber (51) and a spark delay vacuum chamber (52); and

a control valve (57; 63) selectively venting said chambers.

16. System to reduce polluting components from the exhaust of internal combustion engines during warmup of the engine, in combination with an engine having an inlet manifold, a throttle, timing control means operable within a predetermined range for timing the ignition of the engine, within said range, with respect to piston position, and an exhaust system including an ex haust manifold, said pollution reducing system comprising means (25, 26, 51, 52) continuously effective during engine operation to adjust the ignition timing of the ignition system within said range;

11 means (24, 27, 28, 53, 54) additionally retarding ignition timing of the ignition system, to a delay value of such magnitude that combustion will persist during at least a portion of the exhaust stroke of the engine in addition to the adjustment of the ignition.

timing, within said range, due to said continuously effective ignition timing means, said additional retarding means being selectively connectable to said ignition timing system;

means (30) responsive to temperature arising in the engine during operation thereof, said temperature responsive means being connected to and controlling said additional ignition timing retardation means and disabling said additional ignition timing retardation means when a predetermined temperature is sensed by said temperature responsive means;

electromagnetically operable valve means (33) controlling air flow through said bypass; and means controlling the opening and closing of said valve means (33);

said valve means being connected to said temperature responsive means (30), said valve means, during the warm-up period of the exhaust system of the engine being open so that said bypass permits air flow is in shunt to the throttles, and said valve means, upon sensing of said predetermined temperature by said temperature responsive means changing to a second state blocking air flow therethrough.

17. System according to claim 16, wherein the means additionally retarding ignition timing of the ignition system comprises a link element (24) connected to adjust the timing of the ignition with respect to piston position;

and means including stop means (27; 54) controlling the path of travel of said link element (24) under control of said temperature responsive means (30).

18. System to reduce polluting components from the exhaust of internal combustion engines during warmup of the engine, in combination with an engine having an inlet manifold, 21 throttle, timing control means op erable within a predetermined range for timing the ignition of the engine, within said range, with respect to piston position, and an exhaust system including an exhaust manifold, said pollution reducing system comprising means (25, 26, 51, 52) continuously effective during enginen operation to adjust the ignition timing of the ignition system within said range;

means (24, 27, 28, 53, 54) additionally retarding ignition timing of the ignition system, to a delay value of such magnitude that combustion will persist during at least a portion of the exhaust stroke of the engine in additioni to the adjustment of the ignition timing, within said range, due to said continuously effective ignition timing means, said additional retarding means being selectively connectable to said ignition timing system;

means (30) responsive to temperatures arising in the engine during operation thereof, said temperature responsive means being connected to and controlling said additional ignition timing retardation means and disabling said additional ignition timing retardation means when a predetermined temperature is sensed by said temperature responsive means;

valve means (33) controlling air flow through said bypass;

a pneumatic pressure sensitive diaphragm operating means (45) connected to operate said valve means and means, including a control valve means (57) interconnecting the pneumatically operating means with differential air pressure (32) to operate said valve means into open position during the warm-up period of the engine and before the engine has reached said predetermined temperature.

19. System according to claim 18, wherein the means additionally retarding ignition timing of the ignition system comprises a link element (24) connected to adjust the timing of the ignition with respect to piston position;

and means including stop means (27; 54) controlling the path oftravel of said link element (24) under control of said temperature responsive means (30).

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1. System to reduce polluting components from the exhaust of internal combustion engines during warm-up of the engine, in combination with an engine having an inlet manifold, a throttle, timing control means operable within a predetermined range for timing the ignition of the engine, within said range, with respect to piston position, and an exhaust system including an exhaust manifold, said pollution reduciNg system comprising means (25, 26, 51, 52) continuously effective during engine operation to adjust the ignition timing of the ignition system within said range, comprising a spark advance vacuum chamber means (25, 26) to advance or delay ignition timing within said range with respect to dead-center position of the piston; adjustment link means (24) connected to the ignition timing adjustment means; means controlling additional retardation of ignition timing of the ignition system, to a delay value of such magnitude that combustion will persist during at least a portion of the exhaust stroke of the engine in addition to the adjustment of the ignition timing, within said range, due to said continuously effective ignition timing means, comprising a control valve (31) interconnecting the spark delay chamber (25) to the inlet manifold of the engine during warm-up time of the engine and before the engine has reached said predetermined temperature, said valve (31) connecting the delay chamber to a suction port (37) located in the vicinity of the throttle (34) in the inlet to the engine; and means (30) responsive to temperature arising in the exhaust system of the engine during operation thereof, said temperature responsive means including means controlling the extent of travel of said link element to disable control by said additional ignition timing retardation means when said temperature responsive means senses that a predetermined temperature is exceeded.
 2. System according to claim 1, wherein the means additionally retarding ignition timing of the ignition system comprises a link element (24) connected to adjust the timing of the ignition with respect to piston position; and means including stop means (27; 54) controlling the path of travel of said link element (24) under control of said temperature responsive means (30).
 3. System according to claim 2, wherein the stop means comprises electromagnetically controlled means (29).
 4. System according to claim 2, wherein the stop means include vacuum diaphragm chamber operated means (42).
 5. System according to claim 4, wherein the temperature responsive means provide an output signal controlling a valve means, said valve means selectively connecting fluids under differential pressure to said vacuum chamber means.
 6. System according to claim 2, wherein said link element (24) is formed with a notch (28), said stop means (27) engaging in the notch.
 7. System according to claim 2 wherein the means continuously effective during engine operation to adjust ignition timing within said range comprises a spark advance vacuum chamber and a spark delay vacuum chamber; and the stop means controlling the path of travel of said link element (24) comprises a movable abutment (54) on said spark delay vacuum chamber movable in dependence on sensed temperature by said temperature responsive means (30) in the direction of said path.
 8. System according to claim 1, wherein the means continuously effective during engine operation to adjust ignition timing within said range comprises a spark advance vacuum chamber and a spark delay vacuum chamber; and wherein the means additionally retarding ignition timing further comprises a vacuum bore (36) located in the inlet (35) to the engine, and means interconnecting said vacuum bore (36) with the spark advance chamber (26); and valve means (31) separating the spark advance chamber from said bore until the engine has reached said predetermined temperature.
 9. System according to claim 8, further comprising means (57) interconnecting the ignition delay chamber (53) with the inlet manifold (32) of the engine until the engine has reached said predetermined temperature.
 10. System according to claim 1, wherein the means continuously effective during engine operation to adjust ignition timing with said range comprises a spark advance vacuum chamber (51) and a spark delay vacuum chamber (52); and a control valve (57; 63) seLectively venting said chambers.
 11. System according to claim 10, wherein said ignition timing retardation means comprises a vacuum chamber (53), said valve meas selectively venting said vacuum chamber.
 12. System to reduce polluting components from the exhaust of internal combustion engines during warm-up of the engine, in combination with an engine having an inlet manifold, a throttle, timing control means operable within a predetermined range for timing the ignition of the engine, within said range, with respect to piston position, and an exhaust system including an exhaust manifold, said pollution reducing system comprising means (25, 26, 51, 52) continuously effective during engine operation to adjust the ignition timing of the ignition system within said range, comprising a spark advance vacuum chamber and a spark delay vacuum chamber; means (31, 33) controlling additional retardation of ignition timing of the ignition system, to a delay value of such magnitude that combustion will persist during at least a portion of the exhaust stroke of the engine in addition to the adjustment of the ignition timing, within said range, due to said continuously effective ignition timing means, and including a vacuum bore (36) located in the inlet (35) to the engine, means interconnecting said vacuum bore (36) with the spark advance chamber, and valve means (31) separating the spark advance chamber from said bore until the engine has reached a predetermined temperature; and means (30) responsive to temperatures arising in the exhaust system of the engine during operation thereof, said temperature responsive means controlling operation of said valve means (31) to disable control by said additional timing retardation means when said temperature resonsive means senses that the predetermined temperature is exceeded.
 13. System according to claim 12, further comprising means (57) interconnecting the ignition delay chamber (53) with the inlet manifold (32) of the engine until the engine has reached said predetermined temperature.
 14. System according to claim 12, wherein the means additionally retarding ignition timing of the ignition system comprises a link element (24) connected to adjust the timing of the ignition with respect to piston position; and means including stop means (27; 54) controlling the path of travel of said link element (24) under control of said temperature responsive means (30).
 15. System according to claim 12, wherein the means continuously effective during engine operation to adjust ignition timing within said range comprises a spark advance vacuum chamber (51) and a spark delay vacuum chamber (52); and a control valve (57; 63) selectively venting said chambers.
 16. System to reduce polluting components from the exhaust of internal combustion engines during warm-up of the engine, in combination with an engine having an inlet manifold, a throttle, timing control means operable within a predetermined range for timing the ignition of the engine, within said range, with respect to piston position, and an exhaust system including an exhaust manifold, said pollution reducing system comprising means (25, 26, 51, 52) continuously effective during engine operation to adjust the ignition timing of the ignition system within said range; means (24, 27, 28, 53, 54) additionally retarding ignition timing of the ignition system, to a delay value of such magnitude that combustion will persist during at least a portion of the exhaust stroke of the engine in addition to the adjustment of the ignition timing, within said range, due to said continuously effective ignition timing means, said additional retarding means being selectively connectable to said ignition timing system; means (30) responsive to temperature arising in the engine during operation thereof, said temperature responsive means being connected to and controlling said additional ignition timing retardation means and disabling said additional ignitiOn timing retardation means when a predetermined temperature is sensed by said temperature responsive means; electromagnetically operable valve means (33) controlling air flow through said bypass; and means controlling the opening and closing of said valve means (33); said valve means being connected to said temperature responsive means (30), said valve means, during the warm-up period of the exhaust system of the engine being open so that said bypass permits air flow is in shunt to the throttles, and said valve means, upon sensing of said predetermined temperature by said temperature responsive means changing to a second state blocking air flow therethrough.
 17. System according to claim 16, wherein the means additionally retarding ignition timing of the ignition system comprises a link element (24) connected to adjust the timing of the ignition with respect to piston position; and means including stop means (27; 54) controlling the path of travel of said link element (24) under control of said temperature responsive means (30).
 18. System to reduce polluting components from the exhaust of internal combustion engines during warm-up of the engine, in combination with an engine having an inlet manifold, a throttle, timing control means operable within a predetermined range for timing the ignition of the engine, within said range, with respect to piston position, and an exhaust system including an exhaust manifold, said pollution reducing system comprising means (25, 26, 51, 52) continuously effective during enginen operation to adjust the ignition timing of the ignition system within said range; means (24, 27, 28, 53, 54) additionally retarding ignition timing of the ignition system, to a delay value of such magnitude that combustion will persist during at least a portion of the exhaust stroke of the engine in additioni to the adjustment of the ignition timing, within said range, due to said continuously effective ignition timing means, said additional retarding means being selectively connectable to said ignition timing system; means (30) responsive to temperatures arising in the engine during operation thereof, said temperature responsive means being connected to and controlling said additional ignition timing retardation means and disabling said additional ignition timing retardation means when a predetermined temperature is sensed by said temperature responsive means; valve means (33) controlling air flow through said bypass; a pneumatic pressure sensitive diaphragm operating means (45) connected to operate said valve means (33); and means, including a control valve means (57) interconnecting the pneumatically operating means with differential air pressure (32) to operate said valve means into open position during the warm-up period of the engine and before the engine has reached said predetermined temperature.
 19. System according to claim 18, wherein the means additionally retarding ignition timing of the ignition system comprises a link element (24) connected to adjust the timing of the ignition with respect to piston position; and means including stop means (27; 54) controlling the path oftravel of said link element (24) under control of said temperature responsive means (30). 